The conventional copy machine fuser roller uses a non-rotating quartz lamp inside the rotating fuser roller core.
The inside of the aluminum core has a black coating to promote heat absorption. All heat transfer to the roller core tube is by radiation from the quartz lamp. This is inefficient and requires higher temperature at the lamp surface to transfer heat for a given power level, than does heat transfer by conduction. The roller also has an outer cover of silicone rubber, Teflon, or another release layer that will operate at high temperature to prevent toner build-up.
Ceramics have been proposed for heater/fuser rollers in Kogure, U.S. Pat. No. 4,813,372 and U.S. Pat. No. 4,801,968; Urban, U.S. Pat. No. 4,810,858; and Yuan, U.S. Pat. No. 5,191,381. The designs in these patents are complex and not readily adapted to present day manufacturing and use. These designs typically place the ceramic layer on the outside of the roller core.
Hyllberg, U.S. Pat. No. 5,408,070, discloses a heater/fuser roller with a thermal regulating layer and a heating layer disposed inside the roller core.
A general object of the present invention is to improve on the prior art ceramic heater roller construction to provide a simple, low cost, easy to manufacture ceramic heater roller with the heater inside a hollow center of the roller core and without a thermal regulating layer of type seen in U.S. Pat. No. 5,408,070.
Recently, energy saving guidelines for copiers have required shorter ramp up times to the fusing temperature (about 200.degree. C., 392.degree. F.), lower idling temperatures to reduce heat losses, and lower heat losses over all.
A further object of the present invention is to provide a ceramic heater/roller with internal heater that provides improved ramp up operation to the fusing temperature.
Hyllberg, U.S. patent application Ser. No. 84,650, issued as U.S. Pat. No. 5,420,395, discloses a roller with electrode bands formed on a heater layer inside of a roller core. It is further object of the invention to improve upon the arrangement disclosed there by providing contact assemblies that fit within the roller and provide continuous electrical connection as the roller is being rotated.